This invention relates to an axial piston engine.
Axial piston engines of the type of this invention are known, for example, from German Patent No. 1,356,798 and European Patent No. 785,359. Such engines are used, for example, as pumps. In pumps of this type a coil spring, counter-mounted on a cylinder drum, presses a shaft ring against a retaining plate to prevent the raising of the sliding blocks, mounted in recesses of this retaining plate, away from the inclined disc during operation of the engine. Various measures have been adopted to counteract the large frictional forces occurring, on the one hand, between the piston ends and the bearing sockets and, on the other hand, between the sliding blocks and the inclined disc.
Thus, it is proposed in German Patent No. 3,627,651 to make the sliding block from a hardened bearing steel and to provide the sliding block with a ceramic material bearing coating on the base or the end face. According to European Patent No. 785,359, the sliding block can be made of a material with high mechanical stability and be provided on the base with sliding bodies which can also partly form the bearing sockets. The bearing sockets can also be lined with a slide-assisting material separately from the base coating. Furthermore, the bearing of the sliding block, which contacts the retaining ring, can be provided with slide-assisting material. Bronze or a leaded bronze alloy is suggested as as such slide-assisting material. It is a disadvantage in the art that the parts of the axial piston engine subjected to friction are only partly lined with specific slide-assisting material, so that the friction occurring hereby is only partially minimised, and thus is less than optimal.
In view of the above state of the art, a basic objective of the invention is to provide an axial piston engine of an otherwise known type without unreasonable construction costs but with minimised friction.
The invention is an axial piston engine having a centrally-located engine shaft, an inclined disc, a plurality of sliding blocks, each having a bearing socket, a retaining ring having an inner face, and a shaft ring having a curved outer face, all disposed peripherally about the centrally-located engine shaft, the curved outer face contacting the inner face of the retaining ring, wherein the retaining ring has an underside with bearing points lined with a slide-assisting material lining of from 9 to 11% wt. Sn, from 8 to 11% wt. Pb, from 0.2 to 1.5% wt. Ni, from 0.1 to 0.3% wt. Fe, from 0.2 to 0.8% wt. Zn, from 0.1 to 0.5% wt. Cd, and from 0.01 to 0.02% wt. Al.
The invention is realised with a uniformly annular disc made of a hard metal, e.g. steel, and has a central circular opening about which a plurality of circular openings are disposed for the sliding blocks. The inner circumference of the central circular opening is suitably frustoconical and is configured almost complimentarily to the outer face of the shaft ring. At least the central bearing point of the retaining ring and/or the bearing sockets and/or the end faces of the sliding blocks are lined with slide-assisting material.
Instead of having to provide the bearing points between the shaft ring and the sliding blocks individually at the sliding blocks, with a slide-assisting material, rather, the retaining ring is thus lined with slide-assisting material at these bearing points suitably in a single operation. The bearing point between the shaft ring and the retaining ring is thereby also provided with slide-assisting material at the same time.
According to a further embodiment of the present invention, the sliding faces of the drum cylinders and the sliding face of the cylinder drum end face are lined with slide-assisting material. Also, the slide-assisting material lining covers the entire surface of the underside of the retaining ring, which has the bearing point with the sliding blocks.
A slide assisting material of the illustrated composition optimally minimizes the friction in the retaining rings.
The slide-assisting material composition suggested for the drum cylinder optimally minimises the friction of the drum cylinder.
Suitably, the slide-assisting material is deposited by the powder coating method, and all of the bearing points can then be provided with the material in a single operation.